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arXiv 2409.07532cond-mat.supr-concond-mat.mes-hall
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平面约瑟夫森结中的多个马约拉纳束缚态及其对无序的鲁棒性

Multiple Majorana bound states and their resilience against disorder in planar Josephson junctions

Pankaj Sharma, Narayan Mohanta

AI总结:

本文研究了平面约瑟夫森结中多个马约拉纳束缚态的局域化特性,发现三种拓扑超导区控制其分布,并证明这些束缚态在二维几何结构中对非磁性无序具有鲁棒性,适量无序反而能减少能级分裂。

摘要:

理论上预测,平面约瑟夫森结在可调的二维几何结构中,于中间金属通道的两端存在零能马约拉纳束缚态(MBS)。我们在此表明,这些平面约瑟夫森结中出现了三种不同的拓扑超导区,它们控制着近零能 MBS 的局域化。受拓扑保护的 MBS 出现在结的狭窄边缘附近——不仅在中间金属通道中,而且在超导引线中也存在,这些引线的宽度与最近实验中使用的数值相似。我们引入化学势的随机涨落,以研究非磁性无序对 MBS 在不同拓扑区域内局域化的影响,并发现由于二维几何结构,MBS 对无序具有相当强的鲁棒性。有趣的是,适量的无序减少了 MBS 对之间的能级分裂,这可能是通过最小化 MBS 的波函数重叠来实现的。我们还讨论了改变超导引线宽度时拓扑超导相的变化。我们的结果揭示了在实验上可实现的平面约瑟夫森结中,受拓扑保护的多个 MBS 局域化的丰富结构,并呼吁对其进行实验验证。

英文摘要:

Planar Josephson junctions are theoretically predicted to harbor zero-energy Majorana bound states (MBS) in a tunable two-dimensional geometry, at the two ends of the middle metallic channel. Here we show that three distinct topological superconducting regimes, governing the localization of the near-zero-energy MBS, appear in these planar Josephson junctions. The topologically-protected MBS appear near the narrow edges of the junction -- not only in the middle metallic channel but also in the superconducting leads which have widths similar to the values used in recent experiments. We incorporate random fluctuation in the chemical potential to investigate the influence of non-magnetic disorder on the localization of the MBS in different topological regimes and find that the MBS are quite robust against disorder because of the two-dimensional geometry. Interestingly, moderate amount of disorder reduces the splitting between the MBS pairs, possibly by minimizing the wave function overlap of the MBS. We also discuss the changes in the topological superconducting phases when the superconducting lead width is varied. Our results reveal a rich structure of the localization of topologically protected multiple MBS in experimentally-accessible planar Josephson junctions, and call for their experimental confirmation.

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